The most nearly pertinent prior art includes several machines for grooving, slitting or slotting pavement that are intended to be mounted on the boom of a road working or earth working machine. A recent example of these is U.S. Pat. No. 4,761,038, to Hackmack, issued Aug. 2, 1988. The machine disclosed by Hackmack is supported on pavement traversing rollers which are so mounted on adjustable frame arms as to provide for heightwise positioning of the axis of the rotary digging instrumentality, for controlling depth of cut. The arrangement is such that the frame arms tend to interfere with access to the digging instrumentality notwithstanding that no housing or enclosure for it is disclosed. Since the digging instrumentality of a machine of this type rotates at a fairly high speed (100-200 rpm), it tends to throw particles of pavement in practically all directions and thus endangers nearby persons and property unless it is substantially completely enclosed. On the other hand, when the digging instrumentality comprises a drum that has picks projecting substantially radially from its cylindrical surface, it is desirable that each pick be received in a socket that provides for its free rotation relative to the drum, for automatic equalization of wear on the picks; and therefore the drum should be readily accessible for regular lubrication of the pick sockets to facilitate such rotation.
The Hackman patent points out the advantages of arranging a planning machine to be carried by an earth working or road working machine that can provide a source of energization for the rotary digging instrumentality of the planning machine and can propel it for movement along the pavement during its operation. This allows the planning machine to be simple and inexpensive and at the same time increases the versatility and utility of the machine that serves as the carrying vehicle, which might otherwise stand idle while the planning machine is in use. As brought out in Hack mack and other references (e.g., U.S. Pat. No. 3,219,388 to Haynes; U.S. Pat. No. 3,829,161 to Wirtgen) the carrying vehicle may be a road scraper or a machine that has some type of boom or lift are arrangement. However, the type of machine most suitable for serving as a carrying vehicle is undoubtedly a front end loader, since such a machine is the one most likely to be needed for other purposes at a site where pavement planning is to be performed and is most likely to be part of the equipment available to a contractor doing such work. Thus a planning machine can be mounted on the twin lifting arms of a front end loader as a replacement for the bucket conventionally carried by those arms; and then, by forcefully lowering those arms to the point where the front wheels of the carrying vehicles are raised above the pavement, a substantial part of the weight of that vehicle is imposed upon the pavement planing machine for maintaining its digging instrumentality in effective engagement with the pavement, all as suggested by West German published patent application No. 2040890, published in 1971.
As a rule, a front end loader is substantially wider than the pavement slot usually needed for a utility trench, the slot width being on the order of 0.5 m (20-21 inches), which is aobut one-third the width of most front end loaders. The obvious position for a planning machine carried by a front end loader is midway between its lift arms, on the longitudinal centerline of the vehicle, since this position is most convenient for the operator under most conditions. However, it is often necessary to cut a pavement slot closely alongside a curb or wall, and here a pavement planning machine centered on a wide front end loader could not be used satisfactorily. In such a situation, too, it is usually desirable to feather or bevel the edge of the slot that is adjacent to the upright surface, to facilitate subsequent repaving. This requires that the axis of the rotary digging instrumentality be tilted out of the horizontal. Since most other operatios will require that the planning machine be operated with that axis horizontal or parallel to the plane of the pavement being worker, provision for tilting adjustment of that axis is obviously desirable.
The weight of a suitable planning machine is well over half a ton and therefore any provision for lateral and tilting adjustments of the machine must include powered means for shifting it in such adjustments. The obvious expedient would be to provide two hydraulic cylinder jacks, one for tilting, the other for lateral shifting, but it is also obvious that such an arrangement would be costly and complicated.
The prior art known to the applicant offers no suggestion for a planning machine adapted to be carried by a front end loader that is both laterally and tiltingly adjustable; much less is there any suggestion of simple, inexpensive and efficient means for accomplishing such dual adjustments.